This invention relates to a portable painkilling system which is attached to a patient""s body.
Analgesics play an important role in pain control and in cases involving chronic pain. It has heretofore been necessary for a patient to be hospitalized or visit a hospital as an out-patient for a long time.
The need for frequent injection of liquid medicine such as an analgesic or the like is onerous both to a patient and to a hospital in terms of time and efficiency. Consequently, an automatic injection system has been developed which injects liquid medicine to a patient periodically and automatically. However, a conventional system is large and expensive, and it physically limits a patient. Thus, a convenient automatic injection system which does not physically limit an action of a patient and can be applied to in-patients, out-patients, and home-patients has been desired for a long time.
In order to respond to this demand, the present applicant has previously proposed a portable analgesic system (see International Application No. PCT/JP 94/00608: International Public Disclosure No. WO 95/27521). This portable analgesic system comprises: a continuous injector for liquid medicine which continuously discharges liquid medicine through a control path in an outlet portion for a given period of time; a switch-valve detachably connected to an outlet of the injector for shutting off discharge of liquid medicine from the injector; a three-way connector connected to an outlet of the switch valve and having three ways; a flexible, elastic reservoir detachably connected to an end of the three-way connector, the reservoir being adapted to constrict in a normal condition and to expand when liquid medicine from the injector is being charged into the reservoir so as to contain a given quantity of liquid medicine; and a pressure-check valve connected to another way of the three-way connector for opening a flow passage only when a pressure of liquid medicine in the reservoir rises above a given value.
In this portable analgesic system, a continuous injector for liquid medicine having a given volume and a given continuous period of time is prepared beforehand. The continuous injector is charged with a given amount of liquid medicine (3 to 5 cubic centimeters) in accordance with a symptom of a patient. Then, the switch valve is opened and liquid medicine is transferred from the continuous injector to the reservoir over a given long period of time (about 0.5 to 10 hours). A patient can move freely during transfer of liquid medicine, while wearing the system. Duration of transferring liquid medicine from the injector to the reservoir substantially accords with duration of continuing an effect of liquid medicine. When a patient feels a pain, the patient presses the reservoir by oneself to inject liquid medicine from the reservoir through the pressure-check valve to the interior of the patient""s body.
However, since in this portable analgesic system, a pressure and a period of time required for pressing the reservoir are about 350 to 700 mm Hg and about 20 to 200 seconds, respectively, a tired patient needs to work hard. Also, if a patient stops pressing the reservoir in the course of pressing, a medical licensee cannot know how much of the liquid medicine has been injected from the reservoir into the patient""s body. Consequently, it is difficult to control the supply of liquid medicine.
In order to overcome this problem, the present applicant has further proposed a portable analgesic system (see International Application No. PCT/JP 99/02699: International Public Disclosure No. WO 00/71190). This portable analgesic system comprises: a continuous injector for liquid medicine which continuously discharges liquid medicine through a control path in an outlet portion for a given period of time; a three-way connector connected to an outlet of the injector and having three ways; a reservoir detachably connected through a flexible tube to an middle end of the three-way connector, the reservoir being adapted to constrict in a normal condition and to expand when another liquid medicine from the injector is being charged into the reservoir so as to contain liquid medicine; and an ON-OFF clamp connected to the flexible tube for clamping and releasing the flexible tube to close and open a flow passage; and a switch valve detachably connected to the other end of the three-way connector for shutting off any discharge of liquid medicine from the injector.
A current portable analgesic system acts effectively in the case where liquid medicine should be injected, at relatively frequent times, into a patient in severe pain. However, in the case where liquid medicine is injected, several times during a relatively long period of time, into a patient in relatively mild pain, a medical licensee or a patient will encounter a new problem, that is, the sterilizing and disinfecting when charging liquid medicine into a continuous injector for liquid medicine or a reservoir is troublesome. In view of the psychology of a patient suffering from pain, it will be effective in medical treatment for him/her to obtain relief and contentment by pressing the reservoir by him/herself.
An object of the present invention is to provide a convenient and portable painkilling system which is attached to a patient""s body and can inject liquid medicine into a patient as many times as required by a patient without the need for sterilizing and disinfecting.
A portable painkilling system in accordance with the present invention comprises: a first continuous injector for liquid medicine which continuously discharges liquid medicine through a control path in an outlet portion for a given period of time; a flexible, elastic reservoir connected to the outlet portion of the first continuous injector for liquid medicine at one end thereof, the reservoir being adapted to constrict in a normal condition and to expand when liquid medicine from the first continuous injector is being charged into the reservoir so as to contain a maximum quantity of liquid medicine; and a second continuous injector for liquid medicine having an inlet portion connected to the other end of the reservoir, the second continuous injector being adapted to receive liquid medicine from the reservoir and to continuously discharge liquid medicine stored in the second continuous, injector through a control path in an outlet portion for a given period of time.
The reservoir in the present invention may be any one of various kinds of reservoirs such as a syringe type reservoir, a bag type reservoir, a bellows type reservoir, a circular button type reservoir, a dome type reservoir, a multi-stepped, button type reservoir, a tandem chamber type reservoir, or the like.
The first and second continuous injectors for liquid medicine which have given volumes and continuous discharge period of time, respectively, the reservoir having a give volume, and the male lure connector are prepared for assembling. The first continuous injector for liquid medicine, the reservoir, and the second continuous injector for liquid medicine are connected in series one after another. A medical licensee charges desired liquid medicine into the first continuous injector by a given quantity in accordance with a symptom of a patient. After the medical licensee removes air from the portable painkilling system, it is attached to a patient""s body, and the outlet portion of the portable painkilling system is coupled to a catheter communicated to the interior of the patient""s body. At this time, liquid medicine has already started to inject liquid medicine continuously from the first continuous injector for liquid medicine into the reservoir. Meanwhile, the patient can move freely while wearing the system on the patient""s body. When a given amount of liquid medicine is charged in the reservoir, flow of liquid medicine from the first continuous injector is automatically stopped due to a pressure of liquid medicine in the reservoir. After the patient confirms that the reservoir is filled with liquid medicine, the patient presses the reservoir to transfer liquid medicine from the reservoir to the second continuous injector. Then, the second continuous injector begins to continuously inject liquid medicine into the interior of the patient""s body. On the other hand, liquid medicine is charged from the first continuous injector into the empty reservoir. This operation is repeated several times over a long period of time until the first continuous injector becomes empty.
For preparation of a next pain, a patient can receive a supplemental liquid medicine in the reservoir at a hospital or in the home by a medical licensee.